21001240240 has 20 divisors (see below), whose sum is σ = 48827883744. Its totient is φ = 8400496064.

The previous prime is 21001240237. The next prime is 21001240277. The reversal of 21001240240 is 4204210012.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 131257672 + ... + 131257831.

Almost surely, 2^21001240240 is an apocalyptic number.

21001240240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001240240 is an abundant number, since it is smaller than the sum of its proper divisors (27826643504).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21001240240 is a wasteful number, since it uses less digits than its factorization.

21001240240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 262515516 (or 262515510 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

Adding to 21001240240 its reverse (4204210012), we get a palindrome (25205450252).

The spelling of 21001240240 in words is "twenty-one billion, one million, two hundred forty thousand, two hundred forty".